Creasing edge with "Subdivision surface" modifier on rounded surface
Actually this is not a bug, this is how it works. Creasing just "pulls" edges on subdivided surfaces towards it's original location (without subsurf) so it's natural.

Please watch this video about 3 different methods regarding the subject:

Tips for Creating Sharp Edges While Modeling

Edit: I may have not been clear enough why that artifact occurs. It's because you're not creasing the edge NEAR the creased one (in the middle which you want to be rounded) and so there is a "jump" between a 100% creased edge and a non-creased edge.